Initially, go look for features; weirpools, deep holes, side streams, overhanging trees, weedbeds, places where people throw lots of food in for the swans, moored boats, bridges- all of these spots will hold fish.
Unfortunately, its not easy to advise in such general terms. Without more specific info from you we cannot offer anything more than general ideas (which don't help that much!). Your best bet will be to choose a particular species to target, or a specific place to fish from, and hopefully the advice will follow.